The present invention relates to a method of treating a liquid material to be treated and in particular to a method of treating a liquid material to be treated, which enables efficient factional removal of toxic materials such as PCB in a liquid mixture and simultaneously enables re-utilization of the separated and removed materials, as well as treatment facilities.
In recent years, there is demand for a reliable method of treating pollutants particularly toxic organic chemicals as a typical factor for damaging the environment. For example, materials such as PCB are chemically stable and thus hardly disposable by decomposition, but because they have strong toxicity and even in a small amount cause adverse effects on living creatures, there is a need for treatment by which such materials are decreased at minute levels. The conventional techniques of treating such materials include thermal chemical decomposition, physiochemical treatment and biological treatment, and for example incineration treatment at temperatures as high as 1200xc2x0 C. or more is mainly used for waste PCB or PCB-containing waste.
However, since this conventional method requires high temperatures, large treatment facilities are required, and further because high-temperature combustion waste gas contains chlorine, secondary toxic materials such as dioxin and benzofuran can be generated upon cooling, which requires special consideration, resulting in the problem of higher costs for treatment facilities as a whole.
In view of the problems in the prior art described above, an object of this invention is to provide a treatment method capable of reliably separating and removing toxic materials at lower facility costs, as well as treatment facilities therefor.
Another object of the present invention is to provide a method of rendering the separated and removed toxic materials re-utilizable as well as facilities therefor.
The object described above is accomplished by the invention described in the claims. That is, the characteristic constitution of the method of treating a liquid material to be treated according to the present invention lies in comprising the step of permitting a liquid treatment material containing materials having different solidifying points to be cooled at a temperature at which desired materials are solidified while others are not solidified and the step of separating the solidified materials from other liquid materials whereby the desired materials are separated.
By doing so, the materials desired to be separated and removed can be reliably separated in a solid form from other liquid components and simultaneously the separation of the desired materials from the remainder in a post-treatment step is made easy, so that no secondary toxic materials are generated and large facilities required in heat treatment are not necessary, thus reducing facility costs and making this method effective for separation and removal of toxic materials.
Further, the step of separating said separated solidified materials from other liquid materials may be conducted by separating from one another by vacuum filtration, and at the time of this separation treatment, a filter aid may be added.
By doing so, the separation of said desired solidified materials from other liquid components is facilitated and promoted, while even if the amount of the materials separated is small, the materials can be more reliably extracted from the treated liquid material by the adsorption action of the filter aid, and said materials can be separated and removed from other liquid components.
Furthermore, it is preferable that after said filter aid is introduced into a vacuum filtration device, a mixture of said solidified materials to be separated and other liquid materials is added to said filter aid.
By doing so, the solidified materials to be separated are certainly adsorbed into the filter aid, while a very small amount of the materials to be separated, which are present as a mixture with liquid components, can be conveniently captured by the filter aid.
Furthermore, it is preferable to conduct the step in which the material to be separated is separated through elution from said filter aid to which said material binds.
By doing so, the aid can be utilized again as a filter aid, and by post-treatment (solidification treatment etc. along with dilution), the separated materials can be conveniently utilized again as e.g. solid fuels.
Then, the characteristic constitution of the treatment facilities for a liquid material to be treated according to the present invention lies in comprising a cooling means capable of permitting a liquid material containing materials having different solidifying points to be cooled at a temperature at which materials desired to be separated are solidified while others are not solidified, a separation means capable of separating the desired solidified materials from other liquid materials to separate the desired materials, and a device for recovering each of the separated materials.
By this constitution, large and complicated facilities required in heat treatment etc. are not necessary for removing the separated materials from the treated liquid material, so the desired materials can be separated reliably at low production costs.
Further, said cooling means may be provided with a primary liquid-cooling tank capable of permitting said liquid material treated to be cooled at low temperatures and a secondary cooling storage tank capable of permitting said liquid material from the primary liquid-cooling tank to be kept cool at low temperatures.
By this constitution, electric energy consumption costs can be conveniently reduced as compared with cooling all at once particularly where a large amount of materials is to be treated.
Furthermore, it is preferable that the means of separating said desired solidified material from other liquid materials is a vacuum filtration device and is provided with a filter aid-feeding means for adding a filter aid to said vacuum filtration device.
By this constitution, the separation of the desired solidified materials from other liquid components is facilitated and promoted, while even if the amount of the desired materials to be separated is small, the materials can be more reliably extracted from the treated liquid material by the adsorption action of the filter aid, and said materials can be separated and removed from other liquid components.
It is preferable that the treatment facilities are provided with a recovery device for recovery and storage of said separated materials from said vacuum filtration device and simultaneously with a means of heating said recovery device to further separate said filter aid from said recovered separated material.
By this constitution, the aid can be utilized again as a filter aid, and by post-treatment (solidification treatment etc. along with dilution), the separated materials can be conveniently utilized again as e.g. solid fuels.